Moscow said Monday it had foiled a new Ukrainian drone attack on a strategic bomber military base hundreds of kilometers from their joint border, as Kyiv called for Russia's ouster from the United Nations, AFP reported.

Russia said it had downed the drone at Engels, a base for the country's strategic aircraft that Kyiv says have been used to strike Ukraine. Three servicemen were killed by falling debris, regional authorities said.

The same day, Russia's domestic security agency said it killed four Ukrainian "saboteurs", who attempted to enter Russia via a border region.

Moscow has accused pro-Kyiv forces of targeting Russian military sites and civilian infrastructure, including blowing up a bridge linking Crimea to Russia.

Russia's defense ministry said on Monday it downed a Ukrainian drone at its Engels airfield in the southern Saratov region located more than 600 kilometers (370 miles) from the border with Ukraine.

It was the second attack on the Engels airfield in less than a month and the deepest strike into Russian territory since President Vladimir Putin started a military operation in Ukraine on February 24.

In early December, the Russian defense ministry said Ukrainian drone attacks caused explosions at two airfields including Engels, leaving three dead. The airfields were targeted with Soviet-made drones, the ministry said at the time.

Separately, Russia's FSB security service said Monday it had killed a group of armed saboteurs from Ukraine that attempted to cross into the Bryansk region carrying "improvised explosive devices".